Prostaglandin F2 alpha (PGF2alpha) is luteolytic when administered to cattle in vivo but luteotropic when incubated with luteal tissue in vitro. A comparison of in vitro effects of PGF2 alpha and two of its analogues suggested the in vitro effect of PGF2 alpha may be due to metabolite(s). Therefore, PGF2 alpha-14C will be incubated with dispersed cell preparations of bovine corpora lutea in an attempt to identify metabolites. Effects of PGF2 alpha on secretion before effects on syntheseis of progesterone were suggested when corpora lutea were removed and incubated with LH 0,2,4 and 8 hours after administration of a luteolytic dose of PGF 2 alpha on secretion rate and the % cell volume occupied by secretion granules will therefore be determined. Effects of PGF2 alpha analogues and estrogens or progesterone concentration of luteal tissue will also be determined. The use of a thermal-conductivity probe to estimate luteal vs. total ovarian blood flow will be evaluated by a comparison to estimates obtained with electromagnetic flow-probes and radioactive microspheres.